The present invention relates to a technology which is effectively applicable to the suppression of coupling noise or crosstalk from the output end of a transmission oscillator in a high frequency IC incorporating a transmission oscillator to other terminals. More particularly, the present invention relates to a technology which is effectively applicable to a high frequency semiconductor integrated circuit device and a wireless electric unit having a phase control loop for phase modulation and an amplitude control loop for amplitude modulation and a wireless communication system, such as cellular phone, incorporating the wireless electric unit.
One of conventional methods for wireless communication equipment (mobile communication equipment), such as cellular phone, is a method designated as GSM (Global System for Mobile Communication). The GSM uses a phase modulation method designated as GMSK (Gaussian Minimum Shift Keying) wherein the phase of carrier waves is shifted according to transmit data.
With respect to recent GSM cellular phones, a system designated as EDGE (Enhanced Data Rates for GMS Evolution) is nearing practical use. The EDGE has 3π/8 rotating 8-PSK (Phase Shift Keying) modulation mode for modulating carrier waves by phase control and amplitude control, in addition to GMSK modulation mode. While one bit of information per symbol is transmitted in GMSK modulation, three bits of information per symbol can be transmitted in 3π/8 rotating 8-PSK (hereafter, referred to as “8-PSK”) modulation. Therefore, in EDGE mode, communication can be carried out at a higher transmission rate than in GMSK mode.
Conventionally, various methods have been known for implementing a modulation method wherein the phase component and the amplitude component of a transmit signal are respectively caused to bear information. One of such methods is that designated as polar-loop transmitter (for example, page 162 of “High Linearity RF Amplifier Design” written by Peter B. Kenington (Artech House, Inc., 1979). In the polar-loop transmitter, a signal to be transmitted is separated into a phase component and an amplitude component, and then these components are respectively fed back with a phase control loop and an amplitude control loop and thereby controlled. Thereafter, the components are synthesized in an amplifier and outputted.
With respect to wireless communication system, efforts have been made in these years to incorporate as many circuits as possible into one or several semiconductor integrated circuits to reduce a number of parts for the reduction of the size and cost of systems. One of such efforts is a technology for incorporating a transmission oscillator into a semiconductor integrated circuit provided with modulating and demodulating functions (hereafter, referred to as “high frequency IC”). With respect to high frequency IC constituting a GSM communication system, that with a transmission oscillator mounted on-chip has been developed and proposed by the present applicants et al. (Patent Document 1).
[Patent Document 1]
Japanese Patent Application No. 2003-048631 (Corresponding U.S. patent application: Ser. No. 10/373,046. Filing data in U.S.: Sep. 13, 2002)